iMac 21" Mid 2010 Model Freezes at the loading screen

Hi,

I have an older iMac (Mid 2010) which was running Mac OS Sierra. I have recently upgraded so I wiped the install and hard drive as recommended, using the Cmd-R approach to get into Disk Utility.

Sadly, each time I now turn it on I get the spinning globe for 10 minutes and the the grey loading screen where the bar eventually fills all the way up but then hangs. I have left the iMac on for a further 24 hours but it simply doesn't load.

Now, none of the Safe Mode or Disk Utility modes work (CMD + R, CMD + R + P etc). I have unplugged the cable for 15 seconds then restarted - still no joy.

Sadly I am out of options and I wondered whether someone could point me in the right direction.

Item specifics

Brand: Apple

Storage Type: HDD (Hard Disk Drive)

Release Year: 2011

Hard Drive Capacity: 500 GB

Memory: 4 GB

MPN: MC309DA

roduct Family: iMac

Type: All-in-OneScreen

Size: 21.5 in

Processor Type: Intel Core i5 2nd Gen. 

Product Identifiers

EAN0885909400706

ProcessorProcessor Speed2.5GHz

DisplayScreen Size21.5in.

Hard DriveHard Drive Capacity500 GB

MemoryManufacturer's RAM Capacity8GB

MiscellaneousForm FactorAll-in-OneRelease DateMay, 2011

Any help would be very gratefully received!

Thanks

Richard